Have you tried using other IDs on the harddisk ? If the hostadapter is switchable and switched to 7, yet responds to ID 6, it is possible that SCSI-ID line 0 is faulty and will not work.
Hence all SCSI-IDs with odd numbers may be inaccessible. Try SCSI-ID 2 or 4 on the harddisk and tell me what happens. :-)